Intranuclear microfilament bundles in the ependymal cells of the third ventricle of the rat

Intranuclear microfilament bundles were observed in ependymal cells of the third ventricle of the rat. The appeared as single, cylindrically-shaped fibrillar bands up to 4.9 micrometer in length. In cross sections of bundles, the microfilaments exhibited an apparently regular arrangement. They were separated by a distance of 4 to 5 nm, measuring approximately 11 nm from centre to centre. One bundle consisted of 55 to 88 microfilaments. The intranuclear bundles terminated at the inner membrane of the nucleus. They exhibited close spatial relationship to perinuclear chromatin, chromatin centres, intrachromatin granules and fibrillar structures. The average ratio of nuclear sections with and without bundles was 1:15.